Rigify wont generate rig
I studied your file and I see there are quite some edits you have made on the metarig. Just for comparison, here's your metarig:



And here's my version, where I only added the Cat metarig (edit note: you used the wolf rig, a little different in the names but that's not a big deal) and moved its bones around to fit your model:



(Note I hid the facial &amp; fingers bones for readability).

See the bones spine.004 and spine.003.
Their heads are in the same position in the raw metarig and in mine, but not in yours. If I separate them in my rig, then I get the same errors you get.
That's one of the things you must pay attention to: when two bones have their heads or tails aligned, you have to preserve that.

In edit mode it's easy, just select both spheres in one shot using a multiselect tool like the circle select. To correct it, you can use vertex snapping (but hide your mesh then) or cursor snapping with &#8679; ShiftS (select one part → &#8679; ShiftS → Cursor to selected, then select the second part → &#8679; ShiftS → Selected to Cursor).

Fix the tail this way and it should work fine.
It works perfectly on my side with your scene so there should be no problem here.

If you need extra edits, then I recommend you to thoroughly study Rigify's manual. It's too long to explain here but the manual does a great job at explaining how to use this addon and also gives tips on how to do things more easy for you and more accurately.

Oh, and... Please correct your bones placement x)



Good luck!